Internal combustion engine ignition system

ABSTRACT

AN INTERNAL COMBUSTION ENGINE IGNITION SYSTEM OF THE TYPE RESPONSIVE TO ALTERNATING CURRENT IGNITION SIGNALS PRODUCED IN TIME RELATIONSHIP WITH THE ENGINE, THE IGNITION COIL PRIMARY WINDING, THE COLLECTOR-EMITTER ELECTRODES OF AN IGNITION COIL PRIMARY WINDING SWITCHING TRANSISTOR AND A CONTROL RESISTOR ARE CONNECTED IN SERIES ACROSS THE BATTERY AND FORWARD BASE-EMITTER CURRENT IS SUPPLIED TO THE SWITCHING TRANSISTOR THROUGH THE COLLECTOR-EMITTER ELECTRODES OF A COIL PRIMARY WINDING SWITCHING TRANSISTOR. A TRIGGER CIRCUIT NORMALLY CONDUCTING CONTROL TRANSISTOR. A TRIGGER CIRCUIT IS RESPONSIVE TO EACH SELECTED HALF CYCLE OF THE ALTERNATING CURRENT IGNITION SIGNALS TO ESTABLISH A SHUNT CIRCUIT WHICH SHUNTS BASE-EMITTER CURRENT FROM THE CONTROL TRANSISTOR TO EXTINGUISH THIS DEVICE AND, CONSEQUENTLY, THE SWITCHING TRANSISTOR WHEREBY THE SWITCHING TRANSISTOR IS OPERATED CONDUCTIVE AND NOT CONDUCTIVE IS TIMED RELATIONSHIP WITH THE ENGINE. ANOTHER TRANSISTOR, RESPONSIVE TO THE POTENTIAL DEVELOPED ACROSS THE CONTROL RESISTOR, SHUNTS BASE-EMITTER CURRENT FROM THE CONTROL RESISTOR, SHUNTS BASE-EMITTER PRIMARY WINDING ENERGIZING CURRENT TO A PREDETERMINED MAGNITUDE AND ANOTHER TRANSISTOR TO LIMIT IGNITION COIL CONTROL POTENTIAL, ESTABLISHES THE ELECTRICAL ANGLE OF EACH CYCLE OF THE ALTERNATING CURRENT IGNITION SIGNALS AT WHICH THE CONTROL TRANSISTOR CONDUCTS TO DETERMINE THE LENGTH OF TIME ENERGIZING CURRENT FLOWS THROUGH THE IGNITION COIL PRIMARY WINDING.

Sept. 20, 1971 P D, E MASTERS ET AL 3,605,713

INTERNAL COMBUSTION ENGINE IGNITION SYSTEM Filed May 18, 1970 2 Sheets-Sheet l DISTRIBUTOR Il m m E Y Ys Q/TCQ i@ l@ Si ATTORNEY Sept. 20, 1971 P. D. I E MASTERS ErAI. 3,605,713

INTERNAL COMBUSTION ENGINE IGNITION SYSTEM Filed May 18, 1970 2 Shoots-Shoot :I

TO POSITIVE POLARITY j# TERMINAL OF BATTERYH j To DISTRIBUTOR .75'

ZZ Ill REsIsToR To R EsIsToR .9/

VOLTS l N VENTORS' ATTORNEY United States Patent U.S. Cl. 123-148E 9 Claims ABSTRACT OF THE DISCLOSURE An internal combustion engine ignition system of the type responsive to alternating current ignition signals produced in time relationship with the engine. The ignition coil primary winding, the collector-emitter electrodes of an ignition coil primary winding switching transistor and a control resistor are connected in series across the battery and forward base-emitter current is supplied to the switchmg transistor through the collector-emitter electrodes of a coil primary winding switching transistor and a control normally conducting control transistor. A trigger circuit 1s responsive to each selected half cycle of the alternating current ignition signals to establish a shunt circuit which shunts base-emitter current from the control transistor to extinguish this device and, consequently, the switching transistor whereby the switching transistor is operated conductive and not conductive in timed relationship with the engine. Another transistor, responsive to the potential developed across the control resistor, shunts base-emitter current from the control transistor to limit ignition coil primary winding energizing current to a predetermined magnitude and another transistor, also responsive to the control potential, establishes the electrical angle of each cycle of the alternating current ignition signals at which the control transistor conducts to determine the length of time energizing current ows through the ignition coil primary winding.

This invention relates to internal combustion engine ignition systems and, more particularly, to a solid state internal combustion engine ignition system which provides for the limiting of ignition coil primary winding energizing current to a predetermined magnitude and establishes the length of time energizing current flows through the ignition coil primary winding.

To provide an adequate ignition sparking potential to the spark plugs of an internal combustion engine, it is necessary that the ignition coil primary winding energizing current reach a predetermined magnitude. However, should the ignition coil primary winding energizing current reach a magnitude greater than is necessary to provide an adequate sparking potential or should the ignition coil primary winding energizing current ow through the ignition coil primary winding for a period of time longer than is necessary, a significant waste of battery power results.

It is, therefore, an object of this invention to provide an improved internal combustion engine ignition system.

It is another object of this invention to provide an improved solid state internal combustion engine ignition system.

It is an additional object of this invention to provide an improved solid state internal combustion engine igni- Patented Sept. 20, 1971 rice tion system which limits the magnitude of energizing current flow through the ignition coil primary winding to a predetermined magnitude and determines the length of time during which energizing current flows through the ignition coil primary winding.

In accordance with this invention, an internal combustion engine ignition system is provided wherein an ignition coil primary winding switching transistor, having control electrode current supplied through a normally conducting control transistor and the current carrying electrodes connected in series with the ignition coil primary winding and a control impedance element across a direct current potential source, is triggered conductive and not conductive in timed relationship with the engine by a trigger circuit responsive to selected half cycles of alternating current ignition signals to establish a shunt circuit which conducts control electrode current from the control transistor to extinguish this device and, consequently, the switching transistor and includes a current limiting transistor, responsive to the potential developed across the control impedance element, which conducts control electrode current from the control transistor to limit the ignition coil primary winding energizing current to a predetermined magnitude and another transistor, also responsive to the control potential, which establishes the electrical angle of each cycle of the alternating current ignition signals at which the control transistor conducts to determine the length of time energizing current ows through the ignition coil primary winding.

For a better understanding of the present invention together with additional objects, advantages and features thereof, reference is made to the following description and accompanying drawings in which:

FIG. 1 sets forth the internal combustion engine ignition system of this invention in schematic form;

FIG. 2 sets forth an alternate embodiment of a portion of the ignition system of FIG. 1 in schematic form; and

FIG. 3 illustrates the alternating current ignition signal wave-form to which the internal combustion engine ignition system of this invention is responsive.

In FIGS. l and 2 of the drawing, like elements have been assigned like characters of reference and the point of reference or ground potential has been schematically illustrated by the accepted symbol and referenced by the numeral 5.

In FIG. 1 of the drawing, the internal combustion engine ignition system of this invention is set forth in schematic form in combination with a source of alternating current ignition signals produced in timed relationship with the engine, referenced by the numeral 15; a direct current potential source, which may be a conventional storage battery 8, and an ignition coil 34 having at least a primary winding 35 and includes at least one ignition coil primary Winding switching transistor 10 having two current carrying electrodes, collector electrode 12 and emitter electrode 13, and a control electrode, base electrode 11; a control impedance element, which may be a variable resistor 14; circuitry responsive to each cycle of the alternating current ignition signals for operating switching transistor 10 conductive and not conductive through the current carrying electrodes in timed relationship with the engine, transistors 20, 30, and 40 and the associated circuitry; circuitry responsive to the control potential developed across control impedance element 14 of the magnitude produced by an ignition coil primary winding energizing current of a predetermined magnitude for limiting the magnitude of energizing current ow through the current carrying electrodes of switching transistor to the predetermined magnitude, transistor 50 and the associated circuitry, and circuitry responsive to the control potential for determining the length of time switching transistor 10 is conductive through the current carrying electrodes during each alternating current ignition signal cycle.

The source of alternating current ignition signals may may be any one of the several conventional magnetic distributors which are well known in the automotive art. One example of a magnetic distributor well known in the automotive art which may be used with the ignition systern circuit of this invention is of the variable reluctance type which is disclosed and described in United States Pat. No. 3,254,247, Falge, which issued May 3l, 1966 and is assigned to the same assignee as that of the present invention. In the interest of reducing drawing complexity, the variable reluctance type ignition distributor disclosed and described in United States Pat. No. 3,254,247 has` been set forth in schematic form in the drawing. A rotor member 16 is rotated in timed relationship with the engine by the engine in a manner well known in the automotive art within the bore of pole piece 17. Equally spaced about the outer periphery of rotor 16 and about the bore of pole piece 17 are a series of projections equal in number to the number of cylinders of the engine with which the distributor and ignition system is being used. Pole piece 17 may be made up of a stack of a number of laminations of magnetic material secured in stacked relationship by rivets or bolts or other fastening methods and the magnetic uX may be provided by a permanent magnet, not shown, which may lbe secured to the lower face surface thereof. As each projection on rotor member 16 approaches a projection on pole piece 17, the reluctance of the magnetic path between pole piece 17 and rotor 16 decreases and as each projection on rotor 16 moves away from a projection on pole piece 17, the reluctance of the magnetic circuit between pole piece 17 and rotor 16 increases. Consequently, the magnetic eld produced by the permanent magnet increases and decreases as each projection on rotor 16 approaches and passes a projection on pole piece 17, a condition which induces an alternating current potential in pickup coil 18, which is magnetically coupled to pole piece 17, of a wave-form as shown in FIG. 3.

Ignition coil 34 may be any one of the several conventional automotive type ignition coils well known in the automotive art having a primary winding 35 and a secondary winding 36 in which the high sparking potential is induced upon the interruption of the energizing circuit of primary winding 35 in a manner to be explained later in this specification.

Without intention or inference of a limitation thereto,

the ignition coil primary winding switching transistor 10 has been illustrated as a type NPN transistor having the usual current carrying electrodes, collector electrode 12 and emitter electrode 13, and a control electrode, base electrode 11.

Control impedance element 14 has been illustrated in the drawing as a variable resistor. It is to be specifically understood, however, that any other suitable electrical impedance element which will provide a potential drop thereacross with current flow therethrough may be substituted therefor without departing from the spirit of the invention.

Upon the closure of movable contact 25 to stationary contact 26 of switch 24, which may be the movable contact and one of the stationary contacts of a conventional automotive type ignition switch well known in the automotive art, the ignition coil primary winding 35, the current carrying electrodes of ignition coil primary' winding switching transistor 10 and control impedance element 14 are connected in series across the direct current potential source through a circuit which may be traced from the positive polarity terminal of battery 8, through movable contact 25 and stationary contact 26 of switch 24, lead 27, ignition coil primary winding 35, the collector-emitter electrodes of ignition coil primary winding switching transistor 10, control impedance element 14 and point of reference or ground potential 5 to the negative polarity terminal of battery 8. The circuit just described is the ignition coil primary winding energizing circuit through which ignition coil primary winding energizing current may flow through ignition coil primary winding 35 and control impedance element 14.

As with conventional automotive type ignition systems, the ignition coil primary winding energizing circuit is established, to build up energizing current ow therethrough to produce a magnetic held, and interrupted to collapse the magnetic eld which induces a high ignition potential in secondary winding 36, in timed relationship with the engine. Consequently, circuitry responsive to alternate half-cycles of the alternating current ignition signals is provided for operating ignition coil primary winding switching transistor 10 conductive and not conductive through the current carrying electrodes in timed relationship with the engine. This circuitry includes a normally conducting type NPN control transistor 20 having a control electrode, base electrode 21, and two current carrying electrodes, collector electrode 22 and emitter electrode 23, through which forward control electrode current is supplied to the ignition coil primary winding switching transistor 10 for producing conduction through the current carrying electrodes of switching transistor 1t] to complete the ignition coil primary winding energizing circuit for the flow of ignition coil primary winding energizing current through the ignition coil primary winding 35 and the control impedance element 14. Forward control electrode current is supplied to type NPN control transistor 20 for conditioning control transistor 20 for conduction through the current carrying electrodes, collector electrode 22 and emitter electrode 23, through a circuit which may be traced from the positive polarity terminal of battery 8, through movable contact 25 and stationary contact 26 of switch 24, lead 27, current limiting resistor 28, collector resistor 37, base resistor 38, the base-emitter electrodes of type NPN control transistor 20, resistor 39 in shunt with the base-emitter electrodes of switching transistor 10, control impedance element 14 and point of reference or ground potential 5 to the negative polarity terminal of battery 8. As the potential of battery 8 is applied across the base-emitter electrodes of type NPN control transistor 20 in the proper polarity relationship to produce base-emitter current flow through a type NPN transistor, base-emitter current ilows through this device through the circuit just described to condition control transistor 20 for conduction through the collector-emitter electrodes thereof. Forward control electrode current is supplied to the ignition coil primary winding switching transistor 10 for producing conduction through the current carrying electrodes of switching transistor 10, collector electrode 12 and emitter electrode 13 to complete the ignition coil primary winding energizing circuit, hereinabove described, for the ow of ignition coil primary winding energizing current through the ignition coil primary winding 35 and control impedance element 14 through a circuit including the current carrying electrodes of control transistor 20 which may be traced from the positive polarity terminal of battery 8, through movable contact 25 and stationary contact 26 of switch 24, lead 27, collector resistor 29, the collectoremitter electrodes of control transistor 20, the base-emitter electrodes of type NPN ignition coil primary winding switching transistor 10, control impedance element 14 and point of reference or ground potential 5 to the negative polarity terminal of battery 8. As the potential of battery 8 is applied across the base-emitter electrodes of type NPN ignition coil primary winding switching transistor 10 in the proper polarity relationship to produce base-emitter current tiow through a type NPN transistor, base-emitter current flows through this device through the circuit just described. As the base-emitter current for ignition coil primary winding switching transistor 10 is supplied through the collector-emitter electrodes of control transistor 20, to trigger the ignition coil primary winding switching transistor 10 conductive and not conductive through the collector-emitter electrodes to establish and intermpt the ignition coil primary winding energizing circuit in timed relationship with the engine, circuitry responsive to each selected half-cycle of the alternating current ignition signals for extinguishing control transistor 20 is provided. To extinguish control transistor 20, a shunt circuit through which the forward control electrode current supplied to control transistor 20 may be shunted from control transistor 20 is provided and includes a device responsive to each selected half-cycle of the alternating current ignition signals for completing this circuit and to each other half-cycle of the alternating current ignition signals for interrupting this circuit whereby the ignition coil primary winding switching transistor 10 is triggered conductive and not conductive through the current carrying electrodes thereof in timed relationship with the engine. This shunt circuit includes the current carrying electrodes, collector electrode 32 and emitter electrode 337 of type NPN transistor 30 and resistor 44 connected in series across junction 45 and point of reference or ground potential 5.

With movable contact 25 closed to stationary contact 26 of switch 24 and with no signal present in pickup coil 18, variable resistor 46 is adjusted until type NPN transistor 40 does not conduct through the current carrying electrodes, collector electrode 42 and emitter electrode 43. That is, the resistance of variable resistor 46 is increased until the potential appearing across junction 47 and point of reference or ground potential is of an insufficient magnitude to break down the base-emitter junction of transistor 40, consequently, the forward base-emitter current which would be supplied to transistor 40 through variable resistor 46 and base resistor 48 is shunted from transsistor 40 through diode 49, pick-up coil 18, resistor 54 and emitter resistor 55 to point of reference or ground potential 5. With transistor 40 not conductive, the potential of battery 8 is applied across the base-emitter electrodes of type NPN transistor 30 in the proper polarity relationship to produce base-emitter current through a type NPN transistor. Consequently, forward base-emitter current tiows through type NPN transistor 30 through a circuit which may be traced from the positive polarity terminal of battery 8, through movable contact 25 and stationary contact 26 of switch 24, lead 27, resistor 28, resistor 56, base resistor 64, the base-emitter electrodes of transistor 30, resistor 44 and point of reference or ground potential 5 to the negative polarity terminal of battery 8. As the collector-emitter electrodes of type NPN transistor 30 are forward poled, this device conducts through the collectoremitter electrodes thereof to complete the shunt circuit through which forward control electrode current is shunted from type NPN control transistor 20, consequently, control transistor 20 is not conductive. With control transistor 20 not conducting, the circuit through which baseemitter electrode current is supplied to ignition coil primary winding switching transistor 10 is interrupted, consequently, switching transistor 10 is not conductive to interrupt the ignition coil primary winding energizing circuit.

When the engine is cranked in a manner well known in the automotive art, rotor 16 of the source of alternating current ignition signals is rotated in timed relationship therewith to produce an alternating current ignition signal in pickup coil of a wave-form as illustrated in FIG. 3 in a manner previously described.

With each half cycle of the alternating current ignition signals during which the potential of terminal end 18a of pickup coil 18 is of a positive polarity with respect to terminal end 18b, diode 49 is reverse biased. Consequently, the potential appearing across junction 47 and point of reference or ground potential 5 is of increased magnitude land of a positive polarity upon junction 47. As this potential is applied across the base-emitter electrodes of type NPN transistor 40 in the proper polarity relationship to produce base-emitter current low through a type NPN transistor, base-emitter current flows through transistor 40` through a circuit which may be traced from the positive polarity terminal of battery 8, through movable contact and stationary contact 26 of switch 24, lead 27, resistor 28, variable resistor 46, base resistor 48, the base-emitter electrodes of type NPN transistor 40, resistor 44 and point of reference or ground potential 5 to the negative polarity terminal of battery 8. Upon the tiow of base-emitter current through type NPN transistor 40, this device conducts through the collector-emitter electrodes thereof to establish a circuit through which forward base-emitter current is shunted around transistor to extinguish transistor 30` which interrupts the shunt circuit through which base-emitter current is shunted away from control transistor 20. Upon the interruption of this shunt circuit, base-emitter current is supplied to control transistor 20, through a circuit previously described, to initiate collector-emitter current ow therethrough to establish the circuit, previously described, through which base-emitter current is supplied to ignition coil primary winding switching transistor '10. The baseemitter current flow through ignition coil primary winding switching transistor 10 initiates collector-emitter current flow therethrough to establish the ignition coil primary Winding energizing circuit, previously described, for the flow of energizing current through primary winding and control impedance element 14. The build-up of energizing current through primary winding 35 produces a magnetic field in a manner well known in the art.

With eaoh half cycle of the alternating current ignition signals during which the potential of terminal end 18a of pickup coil 18 is of the negative polarity with respect to terminal end 18b, diode `49 becomes forward poled to shunt base-emitter current from transistor through the circuit previously described to point of reference or ground potential 5. With base-emitter current shunted away from transistor 40, this device extinguishes to interrupt the circuit through which base-emitter current is shunted around transistor 30. Transistor 30, consequently, conducts through the collector-emitter electrodes thereof to complete the shunt circuit, previously described, through which base-emitter current is shunted from control transistor 20 to extinguish control transistor 20. With control transistor 20` extinguished, the circuit, previously described, through which base-emitter current is supplied to ignition coil primary winding switching transistor 10 is interrupted to extinguish this device, a condition which interrupts the ignition coil primary winding energizing crcuit, previously described. Upon the interruption of the ignition coil primary winding energizing circuit, the magnetic field of ignition coil primary winding 35 collapses to induce `a high ignition potential in ignition coil secondary winding 36 which is directed to the proper spark plug of the engine through a conventional distributor, not shown, in a manner well known in the automobile art.

From this description, it is apparaent that ignition coil primary switching transistor 10 is triggered conductive with each half-cycle of the alternating current ignition signal during which the potential of terminal end 18a of pickup coil 18 is of a positive polarity with respect to terminal end 18b and is triggered not conductive with each half cycle of the alternating current ignition signal during which the potential of terminal end 18a of pickup coil 18 is of `a negative polarity with respect to terminal end 118b.

The device included in the shunt circuit through which base-emitter electrode current is shunted away from control transistor 20 is, of course, transistor 30. Tnansistor 30 is responsive to alternate half-cycles of the alternating current ignition signals for interrupting and establishing this shunt circuit whereby the ignition coil primary winding switching transistor is triggered conductive and not conductive through the current carrying electrodes thereof in timed relationship with the engine. Transistors 3() and 40 lare connected in a trigger circuit configuration for the purpose of providing a sharp switching action with each half cycle of the alternating current ignition signals- To limit the energizing current owing through ignition coil primary Winding 35 to a predetermined magnitude, a current limiting transistor, illustrated as type NPN transistor 5t), having two current carrying electrodes, collector electrode 52 and emitter electrode 53, and a control electrode, base electrode 51, responsive to the control potential developed across control impedance element 14 of the magnitude produced by an ignition coil primary winding energizing current of a predetermined magnitude is provided. Base electrode 51 of current limiting transistor 50 is connected to junction 65 between the emitter electrode 13 of ignition coil primary winding switching transistor and control impedance element 14 through a base resistor 66 and the collector-emitter eletrodes of current limiting transistor 50 are connected across Ajunction 45 between resistor 37 and base resistor 38 and point of reference or ground potential 5, consequently, the control potential developed across control impedance element 14, of a positive polarity upon junction 65 with respect to point of reference or ground potential 5, is applied across the base-emitter electrodes of type NPN current limiting transistor 50 in the proper polarity relationship to produce base-emitter current tlow through a type NPN transistor. The impedance value of control impedance element 14 is selected or adjusted to the value which, with the selected magnitude of energizing current ow through ignition coil primary winding 35, will provide a potential drop thereacross of the magnitude which will initiate base-emitter current ow through type NPN current limiting transistor 50 through a circuit which may be traced from the positive polarity terminal of battery `8, through movable contact and stationary contact 26 of switch 24, lead 27, ignition coil primary winding 35, the collector-emitter electrodes of ignition coil primary winding switching transistor 10, base resistor 66, the base-emitter electrodes of current limiting transistor 50 and point of reference or ground potential 5 to the negative polarity terminal of battery 8. Consequently, when the ow of energizing current through ignition coil primary winding 35 has reached the predetermined magnitude, current limiting transistor 50 is triggered conductive through the collector-emitter electrodes thereof to establish another circuit, which may be traced from junction 45, through leads 67 and 68, the collector-emitter electrodes of current limiting transistor 50 and lead 69 to point of reference or ground potential 5, through which base-emitter current is shunted fromcontrol transistor 20 to reduce the degree of collectoremitter conduction through this device. With reduced collector-emitter conduction through control transistor 20, the magnitude of base-emitter current supplied to ignition coil primary winding switching transistor 10 is reduced, a condition which reduces the magnitude of collector-emitter current ilow through this device which, of course, reduces the magnitude of energizing current ilow through the energizing 'circuit for ignition coil primary winding 35, thus limiting the magnitude of energizing current flow therethrough to the predetermined magnitude.

A thermistor 75 may be connected across the baseemitter electrodes of current limiting transistor 50 for purposes of temperature compensation. Thermistor 75 compensates for Veb change versus temperature of transistor 50.

To determine the length ot time ignition coil primary winding switching transistor is conductive through the current carrying electrodes during each alternating current ignition signal cycle, a circuit responsive to the control potential for establishing the electrical angle of each cycle of the alternating current ignition signals at which control transistor 2() conducts through the current carrying electrodes is provided. This circuit comprises type NPN transistor 60 and 70, each having two current carrying electrodes, respective collector electrodes 62 and 72 and respective emitter electrodes 63 and 73, and a control electrode, respective base electrodes 61 and 71, capacitor 77 and the associated circuitry.

The base electrode I61 of transistor 60 is connected to junction 65 between the emitter electrode 13 of ignition coil primary switching transistor 10 and control impedance element 14 through base resistor 74 and base resistor 66. Consequently, the control potential developed across control impedance element 14 is applied across the base-emitter electrodes of transistor 60 in the proper polarityr relationship to produce base-emitter current ow through a type NPN transistor. The base electrode 71 of transistor is connected to junction S5 between resistor 86 and diode 87 through diode 88. The collectoremitter electrodes of transistor 60 are connected across junction 90 between the base electrode 71 of transistor 70 and capacitor 77 and point of reference or ground potential 5 through collector resistor 91 and emitter resistor 92 and the collector-emitter electrodes of transistor 70 are connected across battery 8 through resistor 28, collector resistor 93 and emitter resistor 55.

As has been brought out earlier in this specilication, control transistor 20 is conductive through the collectoremitter electrodes to supply forward base-emitter current to ignition coil primary winding switching transistor 10 while transistor 40 is conductive through the collector-emitter electrodes and is not conductive through the collector-emitter electrodes thereof to interrupt the circuit through which forward base-emitter current is supplied to ignition coil primary winding switching transistor 10 While transistor 4i) is not conductive through the collector-emitter electrodes. Consequently, the electrical angle of each cycle of the alternating current ignition signals at which control transistor 20 conducts through the collector-emitter electrodes is determined by the electrical angle of each cycle of the alternating current ignition signals at which transistor l40 conducts through the collector-emitter electrodes.

Transistor 40 conducts through the collector-emitter electrodes thereof while the potential of the half cycles of the alternating current ignition signals during which the potential of terminal end 18a of pick-up coil 18 is of a positive polarity with respect to terminal end 18h is of a sufficient magnitude to reverse bias diode 49 and does not conduct through the collector-emitter electrodes thereof with the alternate half cycles of the alternating current ignition signals. The electrical angle of the half cycles of the alternating current ignition signals during which the potential of terminal end 18a of pick-up coil 18 is of a positive polarity with respect to terminal end ISb at which transistor 40 conducts through the collector-emitter electrodes is the electrical angle at which the potential appearing across pick-up coil 18 is of a sutiicient magnitude to reverse bias diode 49. Consequently, this electrical angle may be controlled or selected or adjusted, or changed by inserting a source of bias potential for pick-up coil 18 in series with pick-up coil 18 and poled to aid the ignition signal potential induced in pick-up coil 18 with the half cycles of the alternating current ignition signals during which terminal end 18a is of a positive polarity with respect to terminal end 1813, the greater the magnitude of this bias potential, the earlier during the half cycles of the alternating current ignition signals during which the potential upon terminal end 18a of pickup coil 18 is of a positive polarity with respect to terminal end 18h and vice versa. To supply this bias potential type NPN transistor 70 connected in an emitter follower congtuation is provided.

As the collector electrode 72 of transistor 70 is connected to the positive polarity terminal of battery 8 through collector resistor 93, resistor 28, lead 27, stationary contact 26 and movable contact 25 of switch 24 and the emitter electrode 73 is connected to the negative polarity terminal of battery 8 through emitter resistor 55 and point of reference or ground potential 5, the collector-emitter electrodes of transistor 70 are poled for for- Ward conduction therethrough. With transistor '70 conducting through the collector-emitter electrodes, the potential drop developed across emitter resistor 55 of a positive polarity upon junction 9S with respect to point of reference or ground potential is the bias potential for pick-up coil 18, the greater the degree of collector-emitter conduction through transistor 70, the greater the magnitude of this bias potential. To establish the degree of collector-emitter conduction through transistor 70, capacitor 77 is connected across the base-emitter electrodes thereof. With the half cycles of the alternating current ignition signals during which the potential upon terminal end 18a of pick-up coil 18 is of a positive polarity with respect to terminal 1817, capacitor 77 charges through a circuit which may be traced from terminal end 18a of pick-up coil 18, through capacitor 9'6, resistor 86, diode 88, capacitor 77, point of reference or ground potential 5 and series resistors 55 and 54 to the opposite terminal end 18h of pick-up coil 18. This charge upon capacitor 77 is of a positive polarity upon the plate thereof connected to junction 90 with respect to the opposite plate and is prevented from being drained o through resistor 86, capacitor 96 and pick-up coil 18 during the alternate half cycles of the alternating current ignition signals by diode 88 which is reverse biased thereby. As this potential is applied across the base-emitter electrodes of type NPN transistor 70 in the proper polarity relationship to produce base-emitter current flow through a type NPN transistor, the charge upon capacitor 77 produces baseemitter current ow through transistor 70 to initiate collector-emitter current ow therethrough which produces the bias potential across emitter resistor 55. The degree of collector-emitter conduction through transistor 70 is established by the magnitude of the charge upon capacitor 77, the greater the magnitude of this charge, the greater the degree of base-emitter current, and, consequently, the greater the degree of collector-emitter conduction through transistor 70. The bias potential developed across emitter resistor 5S is directly proportional to the degree of collector-emitter conduction through transistor 70.

The bias potential developed across remitter resistor 55 is in series aiding relationship with the potential of the half cycles of the alternating current ignition signals induced in pick-up coil 18 during which the potential of terminal end 18a of pick-up coil 18 is of a positive polarity with respect to terminal end 18h. Therefore, the sum of the bias potential magnitude and the ignition signal potential magnitude during these half cycles is the magnitude of reverse bias potential across diode 49. Diode 49 is reverse biased off by a reverse bias potential of a specific magnitude, therefore, the greater the magnitude of bias potential, the smaller the magnitude of the ignition signal potential required to reverse bias diode 49 and vice versa.

The control potential developed across Control impedance element 14 is applied across the base-emitter electrodes of type NPN transistor 60 through base resistors 66 and 84 and point of reference or ground potential v5 and emitter resistor 92, respectively, in the proper polarity relationship to produce base-emitter current ow therethrough a type NPN transistor. Should the ignition coil primary winding energizing current reach the predetermined magnitude, the control potential appearing across control impedance element 14 reaches the magnitude which will initiate base-emitter current flow through both type NPN transistors 50 and 60 to initiate collectoremitter current ow therethrough. The collector-emitter current ow through type NPN current limiting transistor 50, of course, drains base-emitter current from control transistor to partially extinguish this device and, in turn, ignition coil primary winding switching transistor 10 in a manner previously explained. The collector-emitter current flow through transistor 60 drains a portion of the charge from capacitor 77 through resistor 91, the collectoremitter electrodes of transistor 60 and resistor 92 to point of reference or ground potential 5 to reduce the magnitude of charge thereon. The reduced magnitude of charge upon capacitor 77 reduces the degree of baseemitter current ow and, consequently, collector-emitter conduction through transistor 70 to reduce the magnitude of bias potential produced across emitter resistor 55. Therefore, a greater ignition signal potential magnitude of the half cycles of the alternating current ignition signals during which the potential of terminal end 18a of pick-up coil 18 is of a positive polarity with respect to terminal end 18b is required to reverse bias diode 49. As this required greater ignition signal potential magnitude is reached later during each cycle of the alternating current ignition signals, transistor conducts through the collector-emitter electrodes later during each cycle and, consequently, ignition coil primary winding switching transistor 10 is operated conductive through the collectoremitter electrodes later during each cycle thereby reducing the length of time for the build-up of ignition coil primary winding energizing current. Should the ignition coil primary winding energizing current not reach the predetermined magnitude, transistor would not conduct to drain away a portion of the charge upon capacitor 77. Therefore, this greater charge upon capacitor 77 increases base-emitter current flow and, consequently, collectoremitter conduction through type NPN transistor to increase the magnitude of bias potential produced across emitter resistor 55. Therefore, a smaller ignition signal potential magnitude of the half cycles of the alternating current ignition signals during which the potential of terminal end 18a of pick-up coil 18 is of a positive polarity with respect to terminal end 18b is required to reverse bias diode 49. As this required smaller ignition signal potential magnitude is reached earlier during each cycle of the alternating current ignition signals, transistor 40 conducts through the collector-emitter electrodes earlier during each cycle and, consequently, ignition coil primary winding switching transistor 10 is operated conductive through the collector-emitter electrodes earlier during each cycle, thereby increasing the length of time for the buildup of ignition coil primary winding energizing current. This circuitry, of course, reaches a steady condition at which ignition coil primary winding switching transistor 10 conducts for a period of time just long enough for the ignition coil primary winding energizing current to build up to the predetermined magnitude.

To prevent spurious signals from triggering ignition coil primary winding switching transistor 10I conductive during those periods of time during which it should not conduct, a type NPN transistor 80` having two current carrying electrodes, collector electrode 82 and emitter electrode 83, and a control electrode, base electrode 81, may be employed. Base electrode 81 of transistor 80 is connected to the positive polarity terminal of battery 8 through base resistor 97, collector resistor 29, lead 27, stationary contact 26 and movable contact 2S of switch 24 and emitter electrode 83 is connected to the negative polarity terminal of battery 8 through point of reference or ground potential 5. Therefore, the potential of battery 8 is applied across the base-emitter electrodes of type NPN transistor 80 in the proper polarity relationship to produce base-emitter current through a type NPN transistor. The collector-emitter electrodes of transistor 80y are connected across the base electrode 11 of ignition coil primary winding switching transistor 10 and point of reference or ground potential 5.

Ignition coil primary winding switching transistor 10` should conduct through the collector-emitter electrodes while control transistor 20 is conducting through the collector-emitter electrodes and should not conduct through the collector-emitter electrodes while control transistor 20 is extinguished. With control transistor 20 conducting through the collector-emitter electrodes, forward baseemitter current is drained from transistor 80, consequently, this device is inefective while control transistor 20 is conducting. With control transistor 20 extinguished, however, forward base-emitter current is supplied to transistor 80 in the proper polarity relationship to produce base-emitter current iiow therethrough and condition transistor 80 for collector-emitter current iiow therethrough. Consequently, should any spurious or unwanted signal appear across the base-emitter electrodes of ignition coil primary winding switching transistor 10 of the proper polarity relationship to produce base-emitter current flow through a type NPN transistor, these signals would be shunted to point of reference or ground potential 5 through the collector-emitter electrodes of transistor 80.

In FIG. l of the drawing, the ignition coil primary winding switch is illustrated as a lsingle type NPN transistor 10. It is to be specifically understood that transistor may be replaced by two transistors connected in Darlington pair and connected as shown in FIG. 2, wherein like elements have been given like characters of reference,

which sets forth that portion of the ignition system circuit of this invention involving the ignition coil primary winding switch.

Diode 87 provides a low impedance discharge path for capacitor 96 during those half cycles of the ignition signals during -which terminal end 18a of pick-up coil |18 is of a negative polarity, Zener diode 98 regulates the potential on the low end of resistor 28 and capacitor 99 represses any voltage transients which may appear at terminal 18b of pick-up coil 18.

Throughout this specification, specific transistor types and electrical polarities have been set forth. It is to be specifically understood, however, that alternate transistor types and compatible electrical polarities may be employed without departing from the spirit of the invention.

While a preferred embodiment of the present invention has been shown and described, it will be obvious to those skilled in the art that various modifications and substitutions may 'be made without departing from the spirit of the invention which is -to be limited only within the scope of the appended claims.

We claim:

1. An internal combustion engine ignition system cornprising in combination with a source of alternating current ingition signals produced in timed relationship with the engine, a direct current potential source and an ignition coil having at least a primary winding, at least one ignition coil primary winding switching transistor having two current carrying electrodes and a control electrode,

a control impedance element, means for connecting said ignition coil primary winding, said current carrying electrodes of said switching transistor and said control impedance element in series across said direct current potential source, means responsive to each cycle of said alternating current ignition signals for operating said switching transistor conductive and not conductive through said current carrying electrodes in timed relationship with said engine, first means responsive to the control potential developed across said control impedance element of the magnitude produced by an ignition coil primary winding energizing current of a predetermined magnitude for limiting the magnitude of energizing current ilow through said current carrying electrodes of said switching transistor to the predetermined magnitude, and second means responsive to said control potential for determining the length of time said switching transistor is conductive through said current carrying electrodes during each alternating current ignition signal cycle.

2. An internal combustion engine ignition system comprising in combination with a source of alternating current ignition signals produced in timed relationship with the engine, -a direct current potential source and an ignition coil having at least a primary winding, at least one ignition coil primary winding switching transistor having two current carrying electrodes and a control electrode, a control impedance element, means for connecting said ignition coil primary winding, said current carrying electrodes of said switching transistor and said control impedance element in series across said direct current potential source, a normally conducting control transistor having a control electrode and two current carrying electrodes through which forward control electrode current is supplied to said switching transistor for producing conduction through said current carrying electrodes of said switching transistor to complete an ignition coil primary winding energizing circuit for the low of ignition coil primary winding energizing current through said ignition coil primary winding and said control impedance element, means responsive to each cycle of said alternating current ignition signals for extinguishing said control transistor whereby said ignition coil primary winding switching transistor is operated conductive and not conductive through said current carrying electrodes in timed relationship with said engine, rst means responsive to the control potential developed across said control impedance element of the magnitude produced by an ignition coil primary winding energizing current of a predetermined magnitude for limiting the magnitude of energizing current flow through said current carrying electrodes of said switching transistor to the predetermined magnitude, and second means responsive to said control potential for establishing the electrical angle of each cycle of said alternating current ignition signals at which said control transistor conducts through said current carrying electrodes.

3. An internal combustion engine ignition system comprising in combination with a source of alternating current ignition signals produced in timed relationship with the engine, a direct current potential source having positive and negative polarity output terminals and an ignition coil having at least a primary winding, at least one ignition coil primary winding switching transistor having two current carrying electrodes and a control electrode, a control irnpedance element, means for connecting said ignition coil primary winding, said current carrying electrodes of said switching transistor and said control impedance element in series across said direct current potential source, a normally conducting control transistor having a control electrode and two current carrying electrodes through which forward control electrode current is supplied to said switching transistor for producing conduction through said current carrying electrodes of said switching transistor to complete an ignition coil primary winding energizing circuit for the How of ignition coil primary winding energizing current through said ignition coil primary Winding and said control impedance element, means responsive to each cycle of said alternating current ignition signals for partially extinguishing said control transistor whereby said ignition coil primary winding switching transistor is operated conductive and not conductive through said current carrying electrodes thereof in timed relationship with said engine, a current limiting transistor having a control electrode and two current carrying electrodes, means for connecting said current carrying electrodes of said current limiting transistor across said control electrode of said control transistor and one polarity output terminal of said direct current potential source, means for applying the control potential developed across said control impedance element of the magnitude produced by an ignition coil primary winding energizing current of a predetermined magnitude across said control electrode and a se lected one of said current carrying electrodes of said current limiting transistor for producing conduction through said current carrying electrodes to reduce the magnitude of forward control electrode current to said control tran` sistor whereby the magnitude of energizing current ow through said current carrying electrodes of said ignition coil primary winding switching transistor is limited to the predetermined magnitude, `and means responsive to said control potential for establishing the electrical angle of each cycle of said alternating current ignition signals `at which said control transistor conducts through said current carrying electrodes.

4. An internal combustion engine ignition system cornprising in combination with a source of alternating current ignition signals produced in timed relationship with the engine, a direct current potential source and an ignition coil having at least a primary winding, at least one ignition coil primary winding switching transistor having two current carrying electrodes, and a control electrode, a control impedance element, means for connecting said ignition coil primary winding, said current carrying electrodes of said switching transistor and said control impedance element in series across said direct current potential source, a control transistor having a control electrode and two current carrying electrodes, a first circuit through which forward control electrode current is supplied to said control transistor for conditioning said control transistor for conduction through said current carrying electrodes, a second circuit including said current carrying electrodes of said control transistor through which forward control electrode current is supplied to said switching transistor for producing conduction through said current carrying electrodes of said switching transistor to cornplete an ignition coil primary winding energizing circuit for the ow of ignition coil primary winding energizing current through said ignition coil primary winding and said control impedance element, a third circuit through which said forward control electrode current supplied to said control transistor may be shunted from said control transistor for extinguishing said control transistor, means included in said third circuit responsive to each selected half cycle of said alternating current ignition signals for completing said third circuit and to each other half cycle of said alternating current ignition signals for interrupting said third circuit whereby said ignition coil primary winding switching transistor is operated not conductive and conductive through said current carrying electrodes thereof in timed relationship with said engine, a current limiting transistor having a control electrode and two current carrying electrodes, means for connecting said current carrying electrodes of said current limiting transistor in shunt across said control electrode of said control transistor and the remainder of said first circuit, means for applying the control potential developed across said control impedance element of the magnitude produced by an ignition coil primary winding energizing current of a predetermined magnitude across said control electrode and a selected one of said current carrying electrodes of said current hunting transistor for producing conduction though said carrying electrodes to reduce the magnitude ot forward control electrode current to said control transistor whereby the magnitude of energizing current flow through said current carrying electrodes of said ignition coil primary winding switching transistor is limited to the predetermined magnitude, and means responsive to said control potential for establishing the electrical angle of each said other half cycle of said alternating current ignition signals at which said third circuit is interrupted.

5. An internal combustion engine ignition system comprising in combination with a source of alternating current ignition signals produced in timed relationship with the engine, a direct current potential source and an ignition coil having at least a primary winding, at least one ignition coil primary winding switching transistor having collector-emitter electrodes and a base electrode, a control impedance element, means for connecting said ignition coil primary winding, said collector-emitter electrodes of said switching transistor and said control impedance element in series across said direct current potential source, a control transistor having a base electrode and collector-emitter electrodes, a rst circuit through which forward base-emitter current is supplied to said control transistor for conditioning said control transistor for conduction through said collector-emitter electrodes, a second circuit including said collector-emitter electrodes of said control transistor through which forward base-emitter current is supplied to said switching transistor for producing conduction through said collectoremitter electrodes of said switching transistor to complete an ignition coil primary winding energizing circuit for the ow of ignition coil primary winding energizing current through said ignition coil primary winding and said control impedance element, a third circuit through which said forward base-emitter current supplied to said control transistor may be shunted from said control transistor for extinguishing said control transistor, means included in said third circuit responsive to each selected half cycle of said alternating current ignition signals for completing said third circuit and to each other half cycle of said alternating current ignition signals for interrupting said third circuit whereby said ignition coil primary winding switching transistor is operated not conductive and conductive through said collector-emitter electrodes in timed relationship with said engine, a current limiting transistor having a base electrode and collector-emitter electrodes, means for connecting said collector-emitter electrodes of said current limiting transistor in shunt across said base electrode of said control transistor and the remainder of said iirst circuit, means for applying the control potential developed across said control impedance element of the magnitude produced by 'an ignition coil primary winding energizing current of a predetermined magnitude across said base-emitter electrodes of said current limiting transistor for producing conduction through said collector-emitter electrodes to reduce the magnitude of base-emitter electrode current to said control transistor whereby the magnitude of energizing current ow through said collector-emitter electrodes of said ignition coil primary winding switching transistor is limited to the predetermined magnitude, and means responsive to said control potential for establishing the electrical angle of each said other half cycle of said alternating current ignition signals at which said third circuit is interrupted.

6. An internal combustion engine ignition system cornprising in combination with a magnetic distributor of the type which produces alternating current ignition signals in a pickup coil in timed relationship with the engine, a direct current potential source having positive and negative polarity output terminals and an ignition coil having at least a primary winding, at least one ignition coil primary winding switching transistor having two current carrying electrodes and a control electrode, a control impedance element, means for connecting said ignition coil primary winding, said current carrying electrodes of said switching transistor and said control impedance element in series across said direct current potential source, a control transistor having a control electrode and two current carrying electrodes, means for connecting said control electrode and a selected one of said current carrying electrodes of said control transistor across said direct current potential source, means for connecting said current carrying electrodes of said control transistor and said control electrode and a selected one of said current carrying electrodes of said switching transistor in series across said direct current potential source, rst and second transistors each having two current carrying electrodes and a control electrode, rst and second resistors, means for connecting said first resistor, said current carrying electrodes of said first transistor and said second resistor in series across said direct current potential source in that order, means for connecting said control electrode and a selected one of said current carrying electrodes of said first transistor across said direct current potential source, means for connecting said current carrying electrodes of said second transistor across said control electrode of said control transistor and the junction between one of said current carrying electrodes of said first transistor and said second resistor, means for connecting said control electrode of said second transistor to the junction between said first resistor and one of said current carrying electrodes of said first transistor, a current limiting transistor having a control electrode and two current carrying electrodes, means for connecting said current carrying electrodes of said current limiting transistor in shunt across said control electrode of said control transistor and one polarity output terminal of said direct current potential source, means for connecting said control electrode of said current limiting transistor to the junction between one of said current carrying electrodes of said switching transistor and said control impedance element, a first diode, means for connecting said control electrode of said first transistor to one terminal end of said pickup coil through said first diode, first and second capacitors, a second diode, means for connecting said first capacitor, said second diode and said second capacitor in series across the junction between said rst diode and one terminal end of said pickup coil and one polarity output terminal of said direct current potential source in that order, third and fourth resistors, means for connecting the other terminal end of said pickup coil to the same polarity output terminal of said direct current potential source through said third and fourth resistors in series, a third transistor having two current carrying electrodes and a control electrode, means for connecting said current carrying electrodes of said third transistor across said direct current potential source through said fourth resistor, means for connecting said control electrode of said third transistor to the junction between said second diode and said second capacitor, a fourth transistor having two current carrying electrodes and a control electrode, means for connecting said current carrying electrodes of said fourth transistor across said second capacitor, and means for connecting said control electrode of vsaid fourth transistor to the junction between one of said current carrying electrodes of said switching transistor and said control impedance element.

7. An internal combustion engine ignition system comprising in combination with a magnetic distributor of the type which produces alternating current ignition signals in a pickup coil in timed relationship with the engine, a direct current potential source having positive and negative polarity output terminals and an ignition coil having at least a primary winding, at least one ignition coil primary winding switching transistor having collector-emitter electrodes and a base electrode, a control impedance element, means for connecting said ignition coil primary winding, said collector-emitter electrodes of said switching transistor and said control impedance element in series across said direct current potential source, a control transistor having a base electrode and collector-emitter electrodes, means for connecting said base-emitter electrodes of said control transistor across said direct current potential source, means for connecting said collectoremitter electrodes of said control transistor and said baseemitter electrodes of said switching transistor in series across said direct current potential source, first and second transistors each hailing collector-emitter electrodes and a base electrode, first and second resistors, means for connecting said `first resistor, said collector-emitter electrodes of said first transistor and said second resistor in series across said direct current potential source in that order, means for connecting said base-emitter electrodes of said first transistor across said direct current potential source, means for connecting said collector-emitter electrodes of said second transistor across said base electrode 0f said control transistor and the junction between said emitter electrode of said first transistor and said second resistor, means for connecting said base electrode of said second transistor to the junction between said first resistor and said collector electrode of said first transistor, a current limiting transistor having a base electrode and collector-emitter electrodes, means for connecting said collector-emitter electrodes of said current limiting transistor in shunt across said base electrode of said control transistor and said negative polarity output terminal of said direct current potential source, means for connecting said base electrode of said current limiting transistor to the junction between said collector electrode of said switching transistor and said control impedance element, a first diode, means for connecting said base electrode of said first transistor -to one terminalend of said pickup coil through said first diode, first and second capacitors, a second diode, means for connecting said first capacitor, said second diode and said second capacitor in series across the junction between said first diode and one terminal end of said pickup coil and said negative polarity output terminal of said direct current potential source in that order, third and fourth resistors, means for connecting the other terminal end of said pickup coil to said negative polarity output terminal of said direct current potential source through said third and fourth resistors in series, a third transistor having collector-emitter electrodes and a base electrode, means for connecting said collector-emitter electrodes of said third transistor across said direct current potential source through said fourth resistor, means for connecting said base electrode of said third transistor to the junction between said second diode and said second capacitor, a fourth transistor having collector-emitter electrodes and a base electrode, means for connecting said collector-emitter electrodes of said fourth transistor across said second capacitor, and means for connecting said base electrode of said fourth transistor `to the junction between said collector electrode of said switching transistor and said control impedance element.

8. An internal combustion engine ignition system comprising in combination with a direct current potential source and an ignition coil having at least a primary winding, means for producing alternating current ignition potential signals in timed relationship with the engine, means responsive to selected polarity half cycles of said alternating current ignition potential signals for establishing an ignition coil primary winding energizing circuit across sad direct current potential source when the potential of each of said selected half cycles reaches a predetermined magnitude and to the other half cycles of said alternating current ignition potential signals for abruptly interrupting said ignition coil primary winding energizing circuit, means for producing a bias potential, means for applying said bias potential to said alternating current ignition potential signals in an aiding relationship during -those said selected half cycles, and means responsive to a predetermined magnitude of ignition coil primary winding energizing current for varying the magnitude of said bias potential in a direction which will result in the establishment of said ignition coil primary winding energizing circuit for a period of time just long enough for the ignition coil primary winding energizing current to reach said predetermined magnitude.

9. An internal combustion engine ignition system cornprising in combination with a direct current potential source and an ignition coil having at least a primary winding, means for producing alternating current ignition potential signals in timed relationship with the engine, means responsive -to selected polarity half cycles of said alternating current ignition potential signals for establishing an ignition coil primary winding energization circuit across said direct current potential source when the potential of each of said selected half cycles reaches a predetermined magnitude and to the other half cycles of said alternating current ignition potential signals for abruptly interrupting said ignition coil primary winding energizing circuit, means responsive to a predetermined magnitude of ignition coil primary winding energizing current for limiting the magnitude of said energizing current to said predetermined magnitude, means for producing a bias potential, means for applying said bias potential to said alternating current ignition potential signals in an aiding relationship during those said selected half cycles, and means responsive to said predetermined magnitude of ignition coil primary winding energizing current for varying the magnitude 0f said bias potential in a direction which will result in the establishment of said ignition coil primary winding energizing circuit for a period of time just long enough for the ignition coil primary winding energizing current to reach said predetermined magnitude.

References Cited LAURENCE M. GOODRIDGE, Primary Examiner U.S. Cl. X.R. 315-209 UNITED STATES PATENT OFFICE CERTIFICATE 0F CORRECTION Patent No. 3 a 605 713 Dated September 20 1971 Paul D. Le Mastersv et al. Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column l, line l5, "time" should read timed line 21, cancel "coil primary winding switching transistor and a Control". Column 3, line l0, cancel "may", second occurrence. Column 6,

Signed and sealed this 9th day of May 1972.

[SEAL] Attest:

EDWARD M. FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents line 55, "crcuit" should read circuit line 62, "apparaent" should read apparent line 68, after "half" insert a Column 9, line 49, "remittei" should read emitter Column ll line 50 "ingition" should read ignition Column 13, a iw line 55, after "said" insert Current Column l6, line 45, TErni should read said 

